U.S. Pat. No. 2,720,679 to Ratliff, discloses a plurality of dam segments that may be individually adjusted so as to provide the desired cross sectional contour of the tire tread being extruded. However, FIG. 6 discloses that the variable dam segments are not disposed upstream from the final die, but in fact, form the final die. A similar die wherein again the adjustable extrusion die appears to be the final die is shown in U.S. Pat. No. 3,195,183 to Phillips.
U.S. Pat. No. 3,323,169 to Vitellaro also discloses a plurality of dam segments which may be adjusted independently with this adjustment being carried out via a motorized adjusting means.
U.S. Pat. No. 3,884,611 to Anderson, et al., discloses an extrusion die wherein a section of the die is thin-walled in construction and extends across the width of the flow channel prior to the outlet from the die. An adjusting mechanism is operative to decrease the cross sectional dimension across a pre-land area by flexing or distorting the thin-walled segment.
U.S. Pat. Nos. 3,940,221 to Nissel and 4,125,350 to Brown are cited for their showing of a controllable die lip so as to control both the position and size of the die lip, with the patent to Nissel further disclosing a control and measuring apparatus.
U.S. Pat. No. 3,870,453 to Howard is cited for its disclosure of an adjustment mechanism for an extruder die having an adjustable and a movable die portion.
U.S. Pat. No. 3,830,610 to Ohkawa, et al., discloses an adjustable contour die having a plurality of vertically adjustable individual upper die sheets for achieving specific contours and a control system for effecting same.